How can we prove that the soul and spirit exist? And how can we differentiate the two?

Answer by Richard Geraghty on 3/4/2013:

Dear Erwin,

The first thing to note is that it is essential for a Catholic to believe that all men have souls or spirits which survive after death and will be judged. After believing this, you are welcome to look for a philosophical proof that all human beings have immortal or spiritual souls which survive after death. The standard philosophical way of doing this is to show that man's ability to reason about the way he should act distinguishes him from the higher animals. This ability is a non-material power. Being non-material, it cannot be poisoned, cut up or be destroyed. Thus it will live forever. The ancient pagan Greek philosophers were the first to make this kind of proof.